Hydrocarbon conversion



Jan. 25, 1944. R. B. DAY ErAL 2,339,915

HYDROGARBON CONVERSION l Filed July 2e, 1940 I yu', vrg,

Patented Jan. 25, 1944 UNITED sTArs AT'ENT OFFICE 2,339,915 y nynnocsnsoN CONVERSION Application July 26, 1940,Se1a1v No. 347,755

(Cl. ISG-52) 6 Claims.

This invention relates to a process for the production of high yields of high octane rating gasoline and more specically to a process involving both thermal and catalytic treatments whereby the hydrocarbon oil to be converted is treated under optimum conditions for conversion to high octane rating gasoline.

Catalytic cracking as ordinarily conducted does not employ recycling of insuiciently converted products to the conversion zone because, as has been found, such insufficiently converted hydrocarbons contain a high percentage of aromatics, cyclo-olens, cyclo-diolens, and diolen hydrocarbon compounds, the tendency of which is to deposit great amounts of carbon or car-'- bonaceous substances upon the catalyst particles, if recycled to the catalyst zone, resulting in a more rapid lowering of catalyst activity than is encountered when passing clean unconverted oils in contact with such catalysts. In order to reduce the formation of carbonaceous substances during conversion, resulting in shorter reactivation times and lower peak reactivating temperatures, it is usual to pass the hydrocarbon oil in contact with the catalyst only once and then thermally crack the insuiciently converted oils in a thermal cracking system. In a process employing both thermal and catalytic cracking in the manner above mentioned, the yield and octane of the gasoline product is good but is not as good as one might expect from a process wherein thev catalytic recycle is also catalytically cracked.

In our invention involving both catalytic and thermal treatments the tWo steps have been combined in a novel and advantageous manner so that a relatively large proportion of the insufciently converted hydrocarbons from the catalytic treatment is subjected to thermal treatment under conditions Which favor the removal of the carbon forming constituents from the insuciently converted hydrocarbons rather than thermal cracking, although some thermal cracking may occur. By this method compounds undesirable in catalytic cracking because of their tendency to form carbon, such as, for example,` diolens, aromatica, cyclo-olens, and cyclodiolens are probably polymerized or undergo some treatment which converts them to higher boiling hydrocarbons which are removed as resiy due from the thermal treating system.

In one specific embodiment the invention comprises iractionating a heavy hydrocarbon. voil charge, together with vaporous reaction productsand catalytic conversion productsboth oi which are formed as hereinafter set forth, to separate fractionated vapors boiling substantially in the range of gasoline from the higher boiling oils, recovering the former, condensing said higher boiling oils as light and heavy reflux condensates in the fractionating zone, commingling a portion of said light reflux condensate with a light oil charging stock, heating and vaporizing the mixture, passing the heated vapors in contact With a mass of granular cracking catalyst, subjecting the catalytic conversion products to fractionation as hereinbefore setriorth, subjecting the residual portion oi said light reflux condensate and said heavy reflux condensate to separate thermal treatments, commingling the conversion products from both thermal treatments, separating non-vaporous liquid residue from .the vaporous reaction products, recovering the former, and subjecting said vaporous reaction products to fractionation ashereinbefore set forth.

f The primary object of this invention is to provide a combination of thermal and catalytic cracking wherein provisions are made for handling heavy distillation residues, such as, for eX- ample, ltopped or reduced crude oils and at the same time 'provide for thermally treating the insufficiently converted hydrocarbons from the catalytic cracking step to effect a removal of undesirable carbon forming constituents contained in the catalytic conversion products, since these materials if returned to the catalytic cracking stepl would result in the formation of large amounts of carbonaceous substances which deposit upon the, catalytic material and lower the activity thereof.

The object ofy the; invention maybe accomplished in the following'mannerr: Heavy charging oil comprising, for example, topped or reduced crude oil isl fractionated, together with the catalytic conversion products and vaporous reaction products from the .thermal treatment, toseparate the'gasoline vapors from the higher boiling oils. Thehi-gher boiling oil, comprising essentially reaction products, 'both catalytic and thermal, and the charging oil are` condensedandA collectedr as. light and heavy reflux condensates. AllV of the lightreiiux. condensate, but preferably" only aportion thereof, may be heated and vaporized and the heated vapors subjected to cata-l lytic cracking. In another man-ner of operation the light reflux condensate subjected to catalytic =cracking is commingled with a relativelyflight hydrocarbon 'oilsuchsas gas oil, naphtha, or kerosene introduced fromi an exterior source, the mixture heated andl vaporized, and the resulting vapors subjected to catalytic cracking, after which the catalytic conversion products may be subjected to fractionation as previously mentioned. The residual portion of the light reux condensate is subjected to thermal treatment un.. der conditions which favor the conversion of carbon forming constituents contained therein into heavier hydrocarbons which are removed as nonvaporous liquid residue in the vaporizing and separating step of the process. Heavy reflux condensate separated as above mentioned, consisting essentially of the heavy oil charge and the heavy ends of the conversion products, is subjected to thermal cracking in a heating oil vand communicating reaction chamber( -The conversion products from both thermal steps are commingled, the mixture supplied to a vaporizing and separating chamber whereinv non-vaporous liquid residue is separated from vaporous reaction products, and the latter subjected to fractionation in the manner previously described.

In the preferred embodiment of the invention a relatively larger portion of the insufficiently converted hydrocarbons formed in both the catalytic and thermal treatments is returned to the thermal treatment as compared to the portion supplied to the catalytic treatment, although in some cases substantially equal amounts may be supplied to each step. By selecting conditions in the thermal treatment which will permit operating in this manner, theoretically at least, the insufficiently converted hydrocarbons make at least one pass through the thermal treating step before being subjected to cracking in the presence of catalytic material. In one or more passes of the insufficiently converted hydrocarbons through the thermal treating step, the undesirable carbon forming constituents which are formed in catalytic cracking are removed and recovered as nonvaporous liquid residue, whereas if these materials were returned-to catalytic cracking a heavy deposition of carbonaceous substances on the catalytic material would result.

The accompanying diagrammatic drawing'illustrates in conventional side elevation one specific form of the apparatus which may be employed to accomplish the objects of the invention.

Referring to the drawing, relatively heavy hydrocarbon oil such as, for example, reduced or topped crude oil or, when desired, a relatively wide boiling range hydrocarbon oil, such as crude oil, is supplied through lline I containing valve 2 to pump 3. Pump 3 discharges through line 4 and when this stream of oil contains light fractions such as, for example, gasoline cr fractions amenable to catalytic cracking in the vapor phase, this stream of hydrocarbon oil in line 4 may be directed through line 5 containing valve 6 into fractionator 1. However, when this stream of hydrocarbon oil contains no lighter hydrocarbons comprising either gasoline or hydrocarbons amenable to catalytic cracking, it may be directed through valve 8 into line 58 for treatment in the manner to be described.

The hydrocarbon oil supplied to fractionator 1 is subjected to fractionation therein in commingled state with vaporous reaction products formed in the subsequent thermal treating step and catalytic conversion products formed in the manner to be described to separate fractionated vapors boiling substantially in the range of gasoline from the higher boiling oils. Fractionated vapors separated as above mentioned leaving fractionator 1 are directed through line El containing` valve I0 to cooling and condensation in condenser I0. Distillate, together with undissolved and uncondensed gases from condenser II, is directed through line I2 containing valve I3 into receiver I4 wherein the distillate and gases are collected and separated. Undissolved and uncondensed gases collected and separated in receiver I4 are removed therefrom by way of line l5 containing valve I6, recovered as a product of the process or subjected to any desired further treatment. A portion of the distillate collected and separated in receiver I4 is returned to the upper portion of fractionator 1 by well known means, not shown, as a reuxing and cooling medium while the residual portion thereof is removed from receiver I4 by way of line I1 containing valve I8, recovered as a product of the process or subjected to any desired further treatment.

Heavy oils separated from the lighter fractionated vapors in fractionator 1, including insuiciently converted hydrocarbons formed in both the thermal and catalytic cracking steps Vas subsequently described and in some cases the heavy portions of the charging oil, are condensed in the fractionator and separated into light and heavy reflux condensates, the light reflux condensate preferably comprising those hydrocarbons boiling below 650 F., while the heavy reflux condensate includes all hydrocarbons boiling above 650 F.

Light reflux condensate separated in fractionator 'I as above mentioned is directed through line I9 containing valve 28 to pump 2|. Pump 2l discharges through line 22 and all of the light reflux condensate may be directed through valve 23 into line 21 and thereafter subjected to catalytic cracking in the manner to be described. Preferably, however, only a portion of the light reflux condensate in line 22 is directed through valve 23 to catalytic cracking while the residual portion thereof is subjected to thermal treatment in the manner to be described. The light reux condensate supplied to line 21 by way of line 22 may be introduced alone to heating coil 29. However, in some cases, it may be commingled with a relatively light hydrocarbon oil, particularly amenable to catalytic cracking, such as, for example, gas oil, naphtha, or kerosene introduced from an exterior source by way of line 24, valve 25, pump 26, line 21, and valve 28 and the mixture supplied to heating coil 2S. When desired, steam and/ or light gaseous products, the latter compris ing either those formed in the process or light gases introduced from an exterior source, are commingled with the hydrocarbon oil in line 21 to aidin substantially completely vaporizing said hydrocarbon oil and also as a means for reducing the total pressure on said oil during treatment. Heating coil 29 receives heat from furnace 30 whereby the oil introduced thereto is substantially completely vaporized and heated to a temperature ranging, for example, from 800 to 1200 F. preferably while maintaining said oil at a pressure ranging, for example, from substantially atmospheric to 20() pounds or more per square inch.

The heated reactants leaving coil 29 are di` rected through line 3| containing valve 32 into reactor 33 which contains catalytic material capable of effecting the desired conversion reaction. In the case here illustrated, reactor 33 may comprise, for example, a zone of the heat exchanger type wherein the catalyst is containedin a plurality of elongated tubular elements of re1- atively small diameter andvwherein-provisionsI are made for passing somesuitable--heat convective lmedium such as combustion gases incontact with the exterior of said elongated tubular elements whereby to supply heat to the reactants during conversion and to effect cooling during reactivation of the mass of catalytic material. Reactor 33, on the other hand, may comprise a cylindrical vessel which is Well insulated to reduce radiation losses and which contains one or a plurality of beds of catalytic material wherein the reaction may be accomplished substantially adiabatically.

In the catalytic cracking of hydrocarbons relatively large amounts of carbonaceous substances are formed which deposit upon the catalytic maf terial thereby reducing its active surface and necessitating reactivation at periodic frequent intervals. The invention contemplates reactivating the used catalytic material in the usual manner, such as, for example, by passing oxygencontaining reactivating gases in contact With the used catalytic material and removing carbonaceous substances as combustion gases along with the spent reactivating gases. It is desirable, therefore, in order that the operation may be carried out as a continuous process to employ at least two reactors, and in some instances more than two reactors, so that While the catalytic material in one reactor is being used for effecting conversion of the hydrocarbon reactants the catalytic material in the other or others may be undergoing reactivation.

Catalysts which have been found to vbe effective in the catalytic cracking of hydrocarbon vapors may comprise pellets or granules of silica or other siliceous and refractory materials composited with compounds selected from the group consisting of alumina, zirconia, and thoria. In addition, the hydrosilicates of alumina, acid treated clays, or the like, have also been found to be effective in the cracking treatment of hydrocarbon vapors. Although the catalysts above recited are generally considered to be the preferred catalysts their use is not to be construed as a limiting feature, for various other catalysts well known to those in the art may be employed within the broad scope of the invention.

The conversion products leaving reactor 33 are directed through line 34 containing valve 35 into line 53, commingling therein with the vaporous reaction products formed in the manner to be described and the mixture supplied to fractionator 'l for treatment in the manner previously described. Fractionator '1, in the case here illustrated, together with the condensing and collecting equipment, may be operated under a superatmospheric pressure ranging, for example, from 25 to 200 pounds or more per square inch.

The residual portion of the light reflux condensate in line 22 is directed through line 35 containing valve 3l to pump 38 which discharges through line 39 containing valve 40 into heating coil 4|, coil 4| receiving heat from furnace 42. Preferably also, in order that substantially all of the insufficiently converted hydrocarbons formed in both the thermal and catalytic treatments may be subjected to some` thermal treatment, thequantity of insufficiently converted hydrocarbons subjected to the thermal treatment as light and heavy reflux condensates should be equal to if not greater than the amount of light reflux condensate directed through valve 23 in line 22 for catalytic cracking in the manner previously described.

' Light reflux condensate passing through coil 4| is subjected toconditionsl of temperature and. l

pressure favorable to the conversion ofV thefu-ndesirable 4compounds present vtherein which .are badcarbon formerswhen brought in contact with 'catalytic material whereby these materialsare converted into heavier hydrocarbons and removed as liquid residue in a subsequent step of. the operation. Temperatures toY which the light-.1reilux condensate may be heated in coil 4| will range from 800 to 1000 F., or thereabouts, while employing a, superatmospheric pressure ranging, for example, from 100 to 1000 pounds or more `per square inch. The heated productsleaving coil 4| by Way of line 43 maybe directed .through line44 containing valve 45 intoline 48 bymeans of Which'they 4are supplied to vaporizing'zand separating chamber for :treatment Vin; the manner vto be described.` Preferably, however, the heated products in line 43 are :directed through valve 46 into reaction chamber 4l, .commingling therein, in some cases, with other yreaction products formed by the thermal crackingof the heavy reflux condensate in the manner to -be described wherein additional time is allowed for the desired reaction to be accomplished. Reac. tion chamber 4l is preferably'operated Yunder a superatmospheric pressure substantially equal :to or slightly less than that employed in coil 4| fand may be insulated to reduce radiation losses` therefrom, although no insulation appears in ithe drawing.

Reaction products leaving reaction chamber '4l comprising those formed in the thermal .cracking of the light reflux condensate and/or those formed in the thermal cracking of the heavy reflux condensate are directed through line' r1.'.8 containing valve 49 into vaporizing and separating chamber 50. In some cases, eitheror both of the reaction products formed in thethermal cracking of the light and heavy reiluxpcondensates may by-pass reaction chamber 4l and, in such cases, these reaction products are .supplied to vaporizing and separating chamber 5|! by way of line 48, having beenintroduced to line 4,8 in the manner described. Chamber 5l! is preferably operated at -a substantially reduced pressure relative to that employed in the heating coil and/or reaction chamber whereby vaporous reaction products supplied thereto are substantially separated from the liquid reaction products and the latter substantially further vaporizedfto form a non-vaporous liquid residue Which is removed by way of line 5| containing valve 52 and recovered as a product of the process or subjected to any desired further treatment. Vaporous reaction products supplied to chamber.` 50, together with vapors evolved therein are directed through line 53 containing valve 54 into Vfractionator 'I for treatment in the manner previously described.

Heavy reflux condensate comprising heavy ends of the conversion products suppliedto fractionator 7 and, in some cases, heavy ends of the charging oil leaving fractionator 'I is directed through line 55 containing valve 56 to pump 51. Pump 51 discharges through line 58 containing valve 53 and, as above mentioned, when the heavy oil charge is not supplied to fractionator l it may be commingled With the heavy -reux condensate in line 58 having been introduced thereto by Way of line 4 inthe manner previously described and the resulting heavy oil mixture supplied to heating coil 60 which receives heat from furnace 6|. rlFhe oil in passing -through coil 60 is raised to a thermal cracking tempera- -ture ranging, forexampla from 800to 10509 F.',-=-or reaction chamber 41 wherein they undergo pro-V longed treatment under the elevated conditions of temperature and pressure in the `manner previously described.

When desired, instead of employing separate thermal treatment of the light and heavy reflux condensates the residual portion of the light reflux condensate supplied to the catalytic cracking step may be subjected to thermal treatment in commingled state with the heavy reflux condensate by directing the residual portion contained in line 22 through line 66 and valve 61 `into line 55 where it combines with the heavy reflux condensate prior to the thermal treatment in coil 60.

An example of one specific operation of the process as it may be accomplished in an apparatus such as illustrated and above described is approximately as follows:

Heavy charging oil comprising a 25 A. P. I. gravity Mid-continent reduced crude oil is fractionated, together with catalytic conversion products and vaporous reaction products, both of which are formed in the manner to be described, to separate fractionated vapors of 400 F. end point from the higher boiling oils, including the heavy ends of the charging stock. The fractionated vapors are subjected to cooling and condensation and the resulting distillate and gas collected and separated.

The higher boiling oils separated from the fractionated vapors are condensed as light and heavy reflux condensates. A portion of the light reflux condensate is commingled with a 33 A. P. I. gravity gas oil in the volumetric ratio of 1:1 and the mixture heated and vaporized at a temperature of 950 F. The heated vapors under a pressure of approximately 30 pounds per square inch are passed in contact with a mass of synthetically prepared silica-alumina catalyst at a liquid hourly space velocity of approximately 2. The resulting catalytic conversion products are fractionated in the manner previously described. l

The residual portion of the light reflux condensate not subjected to catalytic cracking is treated thermally at a temperature of approximately 850 F. and under a superatmospheric pressure of approximately 300 pounds per square inch. The conversion products formed by the thermal treatment of the light reflux condensate are supplied to a vaporizing and separating chamber for treatment in the manner to be described.

Heavy reflux condensate separated as above mentioned is subjected to thermal cracking in a heating coil and communicating reaction chamber at a temperature of 920 F. and under a superatmospheric pressure of 400 pounds per square inch. The conversion products formed in the thermal cracking of the heavy reflux condensate are `commingled with the conversion products formed in the thermal treatment of the light reflux condensate and the mixture supplied to a reduced pressure vaporizing and separating chamber wherein vaporous reaction products are substantially separated from the liquid ref action products and the latter substantially further vaporized to form a non-vaporous liquid residue which ls recovered as a product of the process. Vaporous reaction products, together with vapors evolved within the vaporizing and separating chamber are subjected to fractionation in the manner previously described.

From an operation employing conditions as above mentioned one may obtain approximately 65.0% of 400 F. end point gasoline of approximately 76 octane number, 25.0% of non-vaporous liquid residue of approximately 10 A. P. I. gravity, the balance being principally carbon, gas, and loss.

We claim as our invention:

1. A process for the conversion of hydrocarbon oil which comprises catalytically cracking a relatively light hydracorbon oil in substantially vapor phase, thermally cracking a heavier hydrocarbon oil, combining resultant cracked vapors from the cracking steps, fractionatlng to form light and heavy reflux condensate, recovering the fractionated vapors, returning one portion of the light reflux condensate to the catalytic cracking step, supplying said heavy reflux condensate to the thermal cracking step, thermally cracking another portion of the light reflux condensate, independently of the heavy reflux condensate, under conditions selected to convert undesirable carbon forming materials into liquid residue and to form cracked vapors, separating liquid residue from the cracked vapors, and fractionating the latter together with cracked vapors from the first mentioned thermal cracking step and the catalytic cracking step.

2. The process of claim 1 further characterized in that the light reflux condensate comprises a fraction having an end boiling point not substantially in excess of 650 F.

3. The process of claim 1 further characterized in that the light reflux condensate and the .heavy reflux condensate subjected to thermal cracking comprises a larger quantity than the quantity of light reflux condensate returned to the catalytic cracking step.

4. A process for the conversion of hydrocarbon oil which comprises catalytically cracking said oil in substantially vapor phase, fractionating resultant cracked vapors together with other cracked vapors to form light and heavy reflux condensates, recovering the fractionated vapors,

'dividing the light reflux condensate into at least two portions each comprising hydrocarbons boiling over the entire boiling range of the light reflux condensate, returning one of said portions to the catalytic cracking step, subjecting another of said portions and said heavy reflux condensate to thermal cracking independently of each other under conditions in each of the thermal cracking steps selected to convert undesirable carbon forming materials into liquid residue and to form said other cracked vapors, combining resultant conversion products from the thermal cracking steps, separating liquid residue from the cracked vapors, and fractionating the latter as aforesaid.

5. A process for the conversion of hydrocarbon oil which comprises catalytically cracking said oil in substantially vapor phase, fractionating resultant cracked vapors together with other cracked vapors to form light and heavy reflux condensates, recovering the fractionated vapors, dividing the light reflux condensate into at least two portions each comprising hydrocarbons boiling over the entire boiling range of Ithe light re.

ux condensate, returning one of said portions to the catalytic cracking step, subjecting another of said portions to thermal cracking under conditions selected to convert undesirable carbon forming materials into liquid residue and to form cracked vapors, combining said heavy reflux condensate with a hydrocarbon oil, heavier than the first mentioned oil, subjecting the mixture to thermal cracking independently of the light reflux condensate, combining resultant conversion products from the thermal cracking steps, separating liquid residue from cracked vapors, and subjecting the latter to fractionation as said other cracked vapors.

6. A process for the conversion of hydrocarbon oil which comprises catalytically cracking a relatively light hydrocarbon oil in substantially vapor phase, thermally cracking a heavier hydrocarbon, combining resultant cracked vapors from the cracking steps and fractionating the same along With a relatively Wide boiling range hydrocarbon oil to form light and heavy reux condensates, recovering the fractionated vapors, subjecting said heavy reflux condensate to thermal cracking as said heavier hydrocarbon oil, dividing said light reflux condensate into at least two portions, each comprising hydrocarbons boiling over the full boiling range of the light reiiux condensate, subjecting one of said portions to catalytic cracking as said relatively light hydrocarbon oil, subjecting another of said portions to thermal cracking, independently of said heavy reux condensate, under conditions selected to convert undesirable carbon forming materials into liquid residue and to form cracked vapors, separating liquid residue fromthe cracked vapors, and subjecting the latter to fractionation with the rst mentioned cracked vapors.

ROLAND B. DAY. ELMER R. KANHOFER. 

